The most studied amyloid proteins are Aβ and tau in Alzheimer`s disease (AD), α-synuclein in Parkinson`s disease (PD), superoxide dismutase 1 (SOD1) in amyotrophic lateral sclerosis (ALS), and polyglutamine-rich huntingtin fragments in Huntington`s disease (HD). This evidence concerns the gene MAPT and Alzheimer disease.